High resolution key sensor incorporated in keyboard musical instrument

Abstract

A key sensor incorporated in a keyboard musical instrument has a shutter plate attached to a turnable key and photo-interrupters stationary with respect to a key bed, and the shutter plate has an outer bottom edge and an inner bottom edge oblique with respect to a virtual plane where optical paths of the photo-interrupters are extending so that the shutter plate intermittently crosses the optical paths.

What is claimed is: 
     
       1. A key sensing device for use in a keyboard instrument in which a key is rotatable with respect to a board member from a rest position to an end position, said key sensing device comprising: a plurality of photo-radiating elements and associated photo-electric converting elements, each photo-radiating element and associated photo-electric converting element forming an optical path therebetween and being stationary with respect to said board member, at least two of said optical paths being located on a virtual plane; and   a shutter plate attached to said key, said shutter plate comprising a plurality of edges including at least one smooth, continuous edge that interrupts said at least two of said optical paths as said key rotates from said rest position to said end position, said at least one smooth, continuous edge varying in distance from said virtual plane so that said interruption of said at least two optical paths occurs sequentially.   
     
     
       2. The key sensing device as set forth in claim 1 wherein said at least one smooth, continuous edge defines a part of an outer peripheral configuration of said shutter plate. 
     
     
       3. The key sensing device as set forth in claim 2 wherein said virtual plane is in parallel to said board member. 
     
     
       4. The key sensing device as set forth in claim 2 wherein another of said plurality of edges is oblique to said virtual plane and defines a window in said shutter plate for allowing said at least two optical paths to intermittently pass therethrough, a distance between the edge defining said part of said outer peripheral configuration and said another of said plurality of edges being constant. 
     
     
       5. The key sensing device as set forth in claim 1 wherein said at least one smooth, continuous edge comprises a linear line. 
     
     
       6. The key sensing device as set forth in claim 1 wherein said at least one smooth, continuous edge comprises a non-linear curve. 
     
     
       7. The key sensing device as set forth in claim 6 wherein said non-linear curve defines a part of an outer peripheral configuration of said shutter plate, and other edges of said plurality of edges define a window in said shutter plate for allowing said at least two optical paths to intermittently pass therethrough. 
     
     
       8. The key sensing device as set forth in claim 1 wherein said at least one smooth, continuous edge defines a part of a window in said shutter for allowing said at least two optical paths to intermittently pass therethrough. 
     
     
       9. The key sensing device as set forth in claim 1 wherein a first set of said plurality of edges is oblique to said virtual plane and defines parts of a first window in said shutter plate for allowing said at least two optical paths to intermittently pass therethrough, and a second set of said plurality of edges is oblique to said virtual plane and defines parts of a second window in said shutter plate spaced from said first window for allowing said at least two optical paths to intermittently pass therethrough. 
     
     
       10. The key sensing device as set forth in claim 1 wherein said photo-radiating elements are respectively opposed to said photo-electric converting elements so that said optical paths directly extend therebetween. 
     
     
       11. The key sensing device as set forth in claim 1 further comprising: a plurality of beam forming elements each coupled through an optical fiber to one of said photo-radiating elements; and   a plurality of beam-receiving elements each coupled through an optical fiber to one of said photo-electric converting elements.   
     
     
       12. A key sensor incorporated in a keyboard musical instrument and associated with a key turntable between a rest position and an end position with respect to a board member, comprising: a) a plurality of sets of photo-radiating elements and photo-electric converting elements stationary with respect to said board member, and having respective optical paths extending on a virtual plane between said photo-radiating elements and associated ones of said photo-electric converting elements; and   b) a shutter plate attached to said key, and having a plurality of edges defining a configuration thereof, at least one of said plurality of edges being continuous and intermittently crossing said optical paths while said key is traveling from said rest position to said end position, said at least one of said plurality of edges varied in a distance from said virtual plane, wherein said at least one of said plurality of edges defines a part of an outer peripheral configuration of said shutter plate, another of said plurality of edges being oblique to said virtual plane and defining a window in said shutter plate for allowing said optical paths to intermittently pass therethrough, a distance between the at least one of said plurality of edges defining said part of said outer peripheral configuration and said another edge being varied for canceling a difference in radius of gyration of said key between points where said optical paths cross said edges.   
     
     
       13. A key sensor incorporated in a keyboard musical instrument and associated with a key turntable between a rest position and an end position with respect to a board member, comprising: a) a plurality of sets of photo-radiating elements and photo-electric converting elements stationary with respect to said board member, and having respective optical paths extending on a virtual plane between said photo-radiating elements and associated ones of said photo-electric converting elements; and   b) a shutter plate attached to said key, and having a plurality of edges defining a configuration thereof, at least one of said plurality of edges being continuous and intermittently crossing said optical paths while said key is traveling from said rest position to said end position, said at least one of said plurality of edges varied in a distance from said virtual plane, wherein said virtual plane is oblique to said board member, and said at least one of said plurality of edges defines one of a part of an outer peripheral configuration of said shutter plate or a part of a window for allowing said optical paths to pass therethrough.   
     
     
       14. A key sensor incorporated in a keyboard musical instrument and associated with a key turnable between a rest position and an end position with respect to a board member, comprising: a) a plurality of sets of photo-radiating elements and photo-electric converting elements for producing light beams therebetween, and operative to output a multi-bit electric signal, said light beams extending on a virtual plane over said board member; and   b) a shutter plate attached to a lower surface of said key, and having an outer bottom edge forming a part of an outer configuration of said shutter plate and oblique to said virtual plane, and   an inner bottom edge forming a part of a window in said shutter plate,     said outer bottom edge and said inner bottom edge intermittently crossing said light beams for changing a bit pattern of said multi-bit electric signal when said key is moved from said rest position to said end position and from said end position to said rest position.